In recent years, in the field of distribution, owing to an increase in the number of handled packages and a decrease in workforce, there has been an increasing need for automation of work. Up to the present, the work of conveyance and sorting of packages has been automated by using a conveyer and a sorter. In addition, automation is progressing as regards the unloading work for putting packages, which are loaded on a pallet box, onto the conveyor. However, when packages with irregular shapes are mixedly present, it is difficult to detect individual packages, leading to a hindrance to automation.
In usual cases, image processing or the like may be used as a package detection method. For example, there is known a package detection apparatus which uses a strobe, and a camera which can be synchronized with the strobe. By photographing edge portions of a package with emphasis, it becomes easier to extract the contour of the package, and individual packages are detected based on the detected contours. However, this detection apparatus has such a problem that it is difficult to extract a gap between packages which are put in close contact with each other, with their surfaces being regularly arranged, or it is difficult to detect a plurality of packages, which are put together, as a single pack.
Besides, as regards this detection apparatus, in some cases, when packages are put in contact in a front-and-rear direction, it is not possible to determine a hidden state of a package, for example, to determine which of the packages extends rearwards, and it is not possible to plan a proper holding strategy for holding the packages. Furthermore, in some cases, this detection apparatus may erroneously detect a pattern which is printed on a package, or a label such as a slip, which is attached to a package, as a contour of the package.